Transformer



Aug. 15, 1950 H, FREEMAN 2,518,767

' TRANSFORMER Filed May 15, 1946 FIG. 1.

INVENTOR. ErnesT-H. Freeman Patented Aug. 15, 1950 TRANSFORMER Ernest H. Freeman, Chicago, 111., assignor to Hirsch Epstein and Louis B. Duman, Chicago, Ill.

Application May 13, 1946, Serial No. 669,228

6 Claims. 1

This invention relates to electric transformers and reactors for glow discharge tubes, particularly hot cathode tubes such as the fluorescent tube lighting lamps.

Transformers of the type of the present invention are designed generally to operate two lamps in a circuit including a condenser in series with one of the lamps to produce a, phase difference of the currents of the tube lamps, thereby reducing the flicker and also improving the power factor of the combination.

It is one of the objects of the present invention to provide a simple, compact, sturdy, reliable and inexpensive transformer having the necessary leakage reactance so that the action of either one of the lamps will not adversely affect the other to any substantial extent.

In a transformer of the above mentioned character it is desirable that the windings that supply current to the respective lamps shall be in such relationships to one another and to the primary winding that the action of each lamp will pro-- duce a, minimum effect on the action of the other. Transformers of this type are generally arranged with separate secondaries for the leading and the lagging lamps, respectively, which secondaries are connected in auto transformer relationship with the primary.

It is desirable to have an exceedingly low leak age flux between the primary winding and that secondary which supplies current to the leading lamp, Heretofore it has been proposed to accomplish this result by making the transformer core structure in the form of an elongated, hollow rectangular core on which the primary is divided into two separate coils placed one on one longitudinal leg of the core and the other on the other longitudinal leg or" the core and, in such an arrangement, it has heretofore been further proposed to divide the secondary which supplies l current to the leading lamp into two separate series connected coils one on each of the two longitudinal legs of the transformer core and adjacent the primary. In order to reduce the leakage reactance flux it has been proposed to make the two secondary coils above referred to concentric with the two primary coi s. This has been found to be satisfactory. The cost of a primary coil with the secondary coil concentric therewith, as used in such arrangements where in there are two series connected primary coils and two series connected secondary coils has been, in the main, only a small amount less than the combined costs of separate primary and secondary coils. This is due to the fact that in the transformer structures of the past which were provided with a concentric secondary and primary it was necessary to provide two separate insulated leads from the primary winding and two separate insulated leads from the secondary winding, the primary leads being in the main insulated from the secondary leads because two separate primary windings on the diiferent legs of the core had to be connected in series and two separate secondaries on the different legs of the core had to be connected in series.

It is one of the objects of the present invention to reduce the cost of the concentric coils on a. glow discharge tube transformer by providing an arrangement wherein a single primary coil is used which has concentric therewith a single secondary coil for supplying the current to the leading lamp. These coils are connected in auto transformer relationship. In view of the fact that it is not necessary to connect two separate primaries in series and two separate secondaries in series I have found that the two coils that constitute the respective primary and the secondary for the leading lamp can be wound as a single coil with end taps and one intermediate tap. For instance, if the primary coil is to have, say, 1500 turns and the secondary concentric therewith is to have 1000 turns, then the coil is originally wound with 2500 turns and, during the winding of the coil, a tap is provided at a point 1500 turns from one end of the coil. This tap together with the end of the cOil which is 1500 turns away therefrom constitute the primary leads. The two ends of the coil that are 2500 turns apart constitute the load supply leads with the result that the last 1000 turns on the 2500 turn coil is connected in step-up auto transformer relationship with the first 1500 turns on the coil. This arrangement is, of course, possible only in a, transformer core where the primary winding is in the form of a single coil as distinguished from one in which the primary winding is in the form of two separate series connected coils.

Ihe coil consisting of a primary with its concentric secondary, and another coil which constitutes the secondary for the lagging lamp, are both placed on a transformer core of the shell type, the iron laminations of which are assembled in the usual manner.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawing forming a part thereof,

.-, this description proceeds.

In the drawing:

Figure 1 is a view of a transforme of the pres ent invention illustrated in circuit with two hot cathode glow discharge lamps;

Figure 2 is a diagrammatic view of the circuit of Figure 1; and

Figure 3 is a plan view of one of the core laminations.

Reference may nowbe had more particularly-to the drawings wherein like reference numera designate like parts throughout.

The transformer of the present invention is indicated in general by the reference numeral l and consists of an elongatedgrectangular core. 2 built up of laminations 3.;gEach-lam-ination 3 .is formed of an elongated rectangular sheet of transformer iron which is stamped to form two slots 5 and 6 leaving a central core portion or finger i which extends through the transformer coils in a manner to-Joe more fully set forth as The. lamination is ,rstamped toprovide. verynarrow .slits. 8 and 9.

.Thefinger i eantherefore. be. flexed out of. the

.plane a of the .rest of. .-.the. sheet for insertion through the .coils.

The successive laminations- ,;are assembled,from. opposite sides of the coils sothat theslits 8...9 of. adjacentlaminations are on opposite sides. of the core. The opposite sides .,Ill and ii vofeach lamination are of a combined width equal;to,ior.,somewhat greater. than the width of the central finger i.

- The transformer core has what appearsto be two. separatespaced apartcoils 2 and .53 thereon .with the fingers (,ofthe assembled stack of laminations extending through the coils. The coil lZ -is a single. winding coil that supplies current ,;to thelagging-lamp. The coil I3 is a, double 'ndingcoil consisting in effect of a'single coil with end terminals, indicated at M and J5, and aninterrnediatetapl5. In one constructionthe coil i3 was providedyyith 2570 turns and thetap l 6 was-electrically connected to the coil at a point This . coilil2' in thisinstancehad 1225 turns In view 10f"-the' fact that the coil [Zhad approximately; phalfthenumber of turns of the coil l3 it was vrnadeof approximately half the length thereof so :that both .coilswere of, approximately the same internal and external diameters, thus substantial- ".ly" filling the lateral space. between the center finger I of the transformer laminations and the f longitudinal endstrips.

The leads i4 and'liiwhich constitute the terminals ofthe primary coil 20 are connected across .:a line 25, which may constitute a source of 120 volt 60 cycle commercial alternating current. -'-"I'he secondary :coil i2 is connected in step-up --auto transformer relationshipwith the primary coil 26, as may be seen from the circuit of Figure 2, and then connected to one of the filaments of a hot cathode fluorescent glow discharge lamp '5 2l, which filament is connected to the opposite 'filarnent of the lamp througha usual starter --switch 28, the opposite filament of the lamp being then connected to the line. The secondary.

-2l is connected at its lead l5=to a reactor 30 ="(Fig.' 2) from which the circuit goes to a, condenser 3|, thence in series to the heating filament' 32- of a hot cathode glow discharge fluorescent lamp 33, thence through-a starting. or com- .-at A9 in Figure 1, and are mounted, on a laminated iron core structure .4! which isof the same construction as the core 2 of Figure l.

The transformer l and the reactor and the condenser 3| are all enclosed in a single sheet iron container and the free space is filled with ,the usualtype of tar-like insulating compound. .By providing the reactor 39 and the starting or compensating winding 34 it is possible to use a 5; much smaller, capacity condenser 35 than would otherwise be required. For instance, in one installation the reactor coil 36 had 520 turns and the starting or compensating coil had 365 turns whererthe lamps 23 and 21 were of theAO Watt type and the transformer lwas ofa size such -.;as previously-set. forth. The necessary condenser 3| was of only four microfarads capacity.

It is to be noted that after the starting switch of the leading lamp 33 opens its circuitxthe starting or compensating winding '34,.is1disconnected and only thereactor 3G and condensera3l are in circuit with the lamp.

In compliance with the requirements of;.:the patent statutes I have; here shown anddescribed a preferred embodiment of my invention. .;It is, xhowevento be understood that, the-invention is not limited to the precise constructioni-z -here shown, the same beingqmerely illustrative ofithe principles of the invention. What I consider new and desire to secure byv Letters Patentzis:

' 1. A transformer for two discharge tubegloads, comprising a rectangular core; having: a central core section located between and paralleltojthe j longitudinal sides of the core, a first coil on said "central corev section, saidcoil having terminals and an intermediate .tap, the coil turns between one terminal and the intermediate tap constituting a primary winding and the coil turns,:be

: tween the intermediate tap and the other termi- .nal constitutinga secondary winding connected in step-up auto transformer relationship-to the primary winding for energizing 'vone discharge tube load, and a second coil on said central-core section and spaced'fromithe first coillongitudinally of the core and comprising a second second- .ary winding and less closely coupled to theprimary than is said. first mentioned secondary,--.said

. second coil being also connectedin step-up. auto transformer relationship with said primary .winding forgenergizing another dischargetube load, the connection between the second coil-and .the primary being at said intermediate -tap.

2; A transformer for two discharge tubeloads,

-..comprising a rectangular core having a.--central core section located between and parallel:to. -.thc i longitudinal sides of the core, a firstcoil onsaid central core section and extending therefrom substantially to the longitudinal sides of .the' core,

said coil having terminals and an intermediate tap, the coil turnsgbetweenone terminal and.the intermediate tap constituting, a primarywinding and the coil turns between theintermediate itap' and-the other terminal constituting a secondary .winding connected in step-up -a-uto transformer elationship to the primary winding fora-energizing one discharge tube load, a second 'coil .onsaid central core section and. spaced from the; first =coil longitudinally of the core and, comprising. a

second secondary winding, said second coil being also connected in step-up auto transformer relationship with said primary winding for energizing another discharge tube load, the connection between the second coil and the primary being at said intermediate tap, and a condenser in series with the first one of the secondaries to cause it to take a leading current.

3. Apparatus for operating two discharge tube loads, comprising a transformer having a single primary winding, a secondary winding concentric with the primary winding, a second secondary spaced from the primary and less closely coupled thereto than is the first mentioned secondary, both secondaries being electrically connected to the primary at the same electrical point in step-up auto transformer relationship, a, core for said windings, said core being of an elongated rectangular shape and having a central longitudinally extending core section between and parallel to the longitudinal sides of the core and extending centrally through said windings whereby the windings are embraced by the core, and leads from the respective secondaries for individual connection to different tube circuits.

4. Apparatus for operating two discharge tube loads, comprising a transformer having a single primary winding, a secondary winding concentric with the primary winding, a second secondary spaced from the primary and less closely coupled thereto than is the first mentioned secondary, both secondaries being electrically connected to the primary at the same electrical point in step-up auto transformer relationship, a core for said windings, said core being of an elongated rectangular shape and having a central longitudinally extending core section between and parallel to the longitudinal sides of the core and extending centrally through said windings whereby the windings are embraced by the core, leads from the respective secondaries for individual connection to different tube circuits, a condenser in the circuit of the lead from the first mentioned secondary, and a two coil reactor having an iron core separate from the aforementioned rectangular core, one of the reactor coils being connected in series circuit with the condenser and the other reactor coil having conductor leads therefrom for permitting the selective connection thereof into and out of said series circuit.

5. Apparatus for operating two discharge tube loads, comprising a transformer having a single primary winding, a secondary winding concentric with the primary winding, a second secondary spaced from the primary and less closely coupled thereto than is the first mentioned secondary, both secondaries being electrically connected to the primary at the same electrical point in stepa up auto transformer relationship, a core for said windings, said core being of an elongated rectangular shape and having a central longitudinally extending core section between and parallel to the longitudinal sides of the core and extending centrally through said windings whereby the windings are embraced by the core, leads from the respective secondaries for individual connection to different tube circuits, a condenser in the circuit of the lead from the first mentioned secondary, and a reactor in series with the condenser, said reactor having an iron core and being outside of the magnetic circuit of the transformer.

6. Apparatus for operating two discharge tube loads, comprising a transformer having a single primary winding, a secondary windin concentrio with the primary winding and extending the full length thereof and closely coupled thereto, a second secondary spaced from the primary and less closely coupled thereto than is the first mentioned secondary, both secondaries being electrically connected to the primary at the same electrical point in step-up auto transformer relationship, a core for said windings, said core being of an elongated rectangular shape and having a central longitudinally extending core section between and parallel to the longitudinal sides of the core and extending centrally through said windings whereby the windings are embraced by the core, leads from the respective secondaries for individual connection to different tube circuits, a condenser in the circuit of the lead from the first mentioned secondary, a reactor in series with the condenser, said reactor having an iron core and being outside of the magnetic circuit of the transformer, an additional coil magnetically coupled to the reactor, and a discharge tube starter switch in the circuit of the tube connected in series with the condenser and circuit connections including said switch for connecting said additional coil in the starting circuit of said last mentioned tube and open circuiting said additional coil upon opening of the starting circuit of said last mentioned tube.

ERNEST H. FREEMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,269,978 Kronmiller Jan. 13, 1942 2,298,935 Freeman Oct. 13, 1942 2,337,992 Hall et a1. Dec. 28, 1943 2,354,879 Ranney Aug. 1, 1944 2,370,635 Bridges Mar. 6, 1945 2,382,638 Keiser Aug. 19, 1945 

